Drawknob organ switch



June 24,1969 R. A. BARNARD 3,452,307

DRAWKNOB ORGAN SWITCH F iled Dec. 5, 1967 INVENTOR ROBERT A BARNARDUnited States Patent 3,452,307 DRAWKNOB ORGAN SWITCH Robert A. Barnard,Vancouver, Wash., assignor to Syndyne Corporation, Vancouver, Wash., acorpo ration of Oregon Filed Dec. 5, 1967, Ser. No. 688,178 Int. Cl.H01h 51/28, N66

US. Cl. 335-153 7 Claims ABSTRACT OF THE DISCLOSURE manent magnets fixedto the drawknob stem, making or breaking electrical circuits to achievethe desired selection of organ tone families or related purposes.

In the past, drawknob organ switches have been complex or uncertain inoperation or 'both. The present switch as described in the abstractovercomes the above problems while retaining those qualities which aredesirable in a drawknob organ switch. These qualities include: (1)extended travel of the drawknob to permit easy visual determination ofthe state of the switch, (2) good feel, that is, proper resistance tothe hand when being manually operated, (3) a reliable overcenteringaction with no possibility of accidentally setting the switch in ahalfway position, (4) switch contacts highly resistant to contaminationby dust and other atmospheric conditions, (5) capability of providingmany sets of switch contacts with no increase of complexity, (6) aminimum number of moving parts, and (7) a shape adapted for the mountingof these switches in closely set groups on a panel, and providing forconvenient electrical connections to be made to the switch when it ismounted in such a group.

FIGURE 1 is a longitudinal cross section of the drawknob switch, showingthe drawknob in its in, rearward, position. Except for minor deviationsnoted below, the switch is symmetrical about its longitudinal axis.

FIGURE 2 is a transverse cross section of the drawknob switch throughsection 22 of FIGURE 1, looking toward the front of the switch, andshowing the method of preventing rotation of the drawknob.

The drawknob switch consists of two principal assemblies; a stationarybody and an axially movable drawknob stem.

The stationary body includes a mounting flange part 1 for attaching theswitch to a vertical panel 30, a ferromagnetic solenoid housing parts 3,4 and 5 enclosing solenoid coils 6 and 7 wound on bobbin 8, and a rearhousing 13 supporting a stationary annular permanent magnet 9. Glassenclosed ferromagnetic reed switches, for example 10 and 11 are locatedin longitudinal grooves on the rear housing, and electrical leads fromthe solenoid and the reed switches are attached to lugs, for example,31, on a terminal connector board 12 at which electrical connections tothe drawknob switch are made. The four electrical leads from the twosolenoid coils are brought out through small holes in the ferromagnetichousing and in the rear housing for attachment to the terminal connectorboard. All the parts of the stationary body are fastened rigidlytogether by adhesives or other means. When the rear housing is made ofthermoplastic material, the reed switches may be conveniently fastenedto the 3,452,307 Patented June 24, 1969 rear housing by using heat tobend fins 32 together to partially enclose the reed switches, as shownin FIG- URE '2.

The drawknob stem consists of a knob 21, a ferromagnetic rod 22, taperedat the ends for maximum efliciency, enclosed for support in anonmagnetic tube 23, permanent magnets 24 and 25, and connecting parts26, 27, and 28. All these parts of the drawknob armature are fastenedrigidly together by adhesives or other means. The permanent magnets areannular, for convenience in fastening them to parts 27 and 28.

The drawknob stem is laterally supported and prevented from wobbling bythe solenoid bobbin, in the bore of which the tube 23 of the stem is asliding fit. Axial movement of the stem is limited by the interferencebetween the shoulders of pants 1 and 26, and 8 and 27, which areseparated by felt washers 17 and 18 to absorb impact at the ends of themotion of the drawknob stem. Since labels which may be inscribed on thedrawknob should be kept upright, rotation of the drawknob stem isprevented by a tab 29 on connector part 27, which slides in alongitudinal groove 14 in the rear housing as shown in FIGURE 2.

The spacing between the two stem magnets is approximately equal to thelength of the stationary magnet. When these three permanent magnets areso spaced, and polarized axially as in FIGURE 1, a strong overcenteraction results. Referring to FIGURE 1, the left hand stem magnet isrepelled strongly to the left if its north pole end is slightly to theleft of the north pole end of the stationary magnet, but is forcedstrongly to the right if its north pole end is slightly to the right ofthe north pole end of the permanent magnet. Similar forces are exertedon the right hand stem magnet, and these forces add to drive thedrawknob stem toward the front if it is slightly to the front of thecenter of its travel, and toward the rear if it is slightly to the rearof the center of its travel. These forces also hold the drawknob stemfirmly in its in or out position.

The drawknob may be moved in or out manually, or by actuation of thesolenoid. Energizing the rear coil of the solenoid will cause theferromagnetic bar, and consequently the whole drawknob stem, to bepulled toward the rear, in position, and the front coil similarly canpull the drawknob stern toward its front, out position. The forcesexerted by the solenoid are suflicient to overcome the retaining forcesof the permanent magnets.

Reed switches which are to 'be closed when the drawknob is in its inposition are mounted on the rear housing radially opposite the rearmostposition of the rear stem magnet, and are actuated by flux from thismagnet when it is adjacent to them. Reed switches which are to be closedwhen the drawknob is in its out position are similarly mounted oppositethe frontmost position on the front stem magnet. As many reed switchesmay be used as desired, limited only by the space available around thecircumference of the rear housing.

Although the device which I have described includes two permanentmagnets on the drawknob stem, and one stationary magnet, it is apparentthat the same effects (overcenter forces and reed switch actuation) canbe obtained with the use of only one magnet on the drawknob stem. Thismagnet is to be axially polarized in the same direction as thestationary magnet. In the unstable center position of the switch, thestem magnet is centrally located within the annular stationary magnet,and when displaced from this position in either direction is furtherrepelled from it, providing snap action. If this stem magnet isapproximately equal in length to the stationary magnet, then when thedrawknob is in its in or its out position, the stem magnet will extendsufiiciently far from the stationary magnet to permit the use of theflux from the stem magnet to operate a reed switch.

However, the device which has been illustrated and described, and whichuses two movable magnets, is to be preferred, because of its strongeraction and because it permits a much greater tolerance in thepositioning and sensitivity of the reed switches.

I claim:

1. A drawknob organ switch device comprising a tubular body having anaxis,

a drawknob having a stem axially movable in said body,

said stem including axially oriented permanent magnet means, said bodyincluding axially oriented annular permanent magnet means through whichthe first named magnet means may be moved toprovide overcenter snapaction,

said stem including a ferromagnetic armature axially oriented,

said body including a solenoid coil through which the ferromagneticarmature may be moved,

reed switch means mounted on said body and s located as to be closed bysaid first named magnet means when said first named magnet means is inone position, and not closed by said first named magnet means when saidfirst named magnet means is in another position,

said reed switch means being adapted for opening and closing electricalcircuits in the control system of an organ.

2. A drawknob organ switch device in accordance with claim 1, in whichsaid second named permanent magnet means is an annular permanent magnet.

3. A drawknob organ switch device in accordance with claim 2, in whichsaid first named magnet means is a pair of annular or cylindricalmagnets axially oriented and axially spaced from each other a distancesubstantially equal to the length of said second named magnet means.

4. A drawknob organ switch device in accordance with claim 3, in whichone of said pair of permanent magnets is partially enclosed by saidsecond named magnet means while the other of said pair is spaced fromsaid second named magnet means when said pair of permanent magnets is inone position, and the second named of said pair of permanent magnets ispartially enclosed by said second named magnet means while the firstnamed of said pair of permanent magnets is spaced from said second namedmagnet means when said pair of permanent magnets is in another position.

5. A drawknob organ switch device in accordance with claim 4, in whichsaid reed switch means is an elongate reed switch enclosed in glass andsaid reed switch is mounted on said body parallel-to the axis ofsaid'body.

6. A drawknob organ switch device in accordance with claim 5, in whichsaid stem includes a tube of rigid non-' magnetic material and saidaxially oriented ferromagnetic armature is a ferromagnetic rod fixedwithin said tube.

7. A drawknob organ switch device in accordance with claim 6, inwhichsaid' body includes another solenoid coil, in addition to saidfirst named solenoid coil, through which said ferromagnetic armature maybe moved.

References Cited UNITED STATES PATENTS 3,260,821 7/1966 Yokoo '33s 1s33,284,741 11/1966 Conklin 335-153

